Biaxially Confined Rock Breakage with SCDA: Large-Scale Tests and Numerical Modelling

Soundless chemical demolition agents (SCDA), also known as expansive cement, represent a potentially viable method for fracturing rock without explosives. Traditionally, expansive cement is used for surface applications, such as block splitting in dimension stone quarries and demolition of concrete foundations. For deep underground applications, the major challenge with the use of expansive cement in an excavation face has been the presence of high biaxial stress field that would hinder the development of fractures in a mining face. This study aims to explore how expansive cement can be potentially used for rock fragmentation in deep underground environments. To do so, large-scale tests on 1 m x 1 m x 0.25 m concrete and granite panels with a novel drilling pattern are prepared, instrumented, and tested under biaxial confinement conditions. Test results show that the proposed drill pattern for expansive cement boreholes is capable of fracturing both panels under biaxial stresses. A 3D finite-difference modelling code FLAC3D 7.0 was developed and validated with observed panel breakage process and failure mechanisms. Both large-scale tests and numerical modelling show that expansive cement induces significant fracturing parallel to the loading plane. These findings should lay the groundwork and provide guidelines for the future application of expansive cement to underground hard rock excavations.